1. Field of the Invention
The present invention relates to color photographic sensitive materials having improved color reproduction and particularly to color photographic sensitive materials wherein the quality of the color images are improved by using a compound which has an interlayer color correction effect.
2. Description of the Prior Art
Generally, in incorporated-coupler color photographic sensitive materials, non-diffusion type couplers are added to each photosensitive layer of the photosensitive materials so as to retain their independent functions. In general, these photosensitive materials comprise a photosensitive emulsion layer (BL) which contains a yellow coupler and is sensitive to blue light (rays having a wave length shorter than about 500 nm), a photosensitive emulsion layer (GL) which contains a magenta coupler and is sensitive to green light (rays having a wave length of about 500 to 600 nm) and a photosensitive emulsion layer (RL) which contains a cyan coupler and is sensitive to red light (visible rays having a wave length longer than about 590 nm). In these photosensitive materials, the BL, GL and RL must perform their functions independently. Therefore, the photosensitive materials further comprise middle layers (ML), filter layers (FL) for ultraviolet rays or for rays having a definite wave length range, antihalation layers (AHL) or protective layers (PL), thereby resulting in a superposed structure of two or more layers.
When excellent color reproduction is desired, the BL, GL and RL must perform their functions independently during production of such multi-layer color photographic sensitive materials, on storage of the unexposed sensitive materials or during image exposure and development. In addition, the BL, GL and RL must each have a coupler which has a preferred distribution of spectral sensitivity in a desired wave length range and forms a color image having suitable spectral absorption. However, color photographic sensitive materials developed at present have many defects.
A first defect in the color reproduction is in the spectral absorption characteristics of the developed images obtained by the coupler used. Namely, the coupler not only does not absorb sufficient light in a specific wave length range but also absorbs light in other wave length ranges, for example, in an undesired short or long wave length range. This defect is noticeable in yellow couplers, and in cyan couplers and is particularly noticeable in magenta couplers. This defect gives rise to a narrow color reproduction range, an aberration of the color tone and particularly a decrease of saturation.
A second defect is that color formation of the coupler in the adjacent photosensitive emulsion layer is caused at image development when a certain photosensitive emulsion layer is developed. For example, the cyan coupler in the RL sometimes colors on image development of the GL. This defect is caused by diffusion of the oxidation products of the color developing agent which are formed on development of a certain specified photosensitive layer into the adjacent photosensitive layer to cause coloring thereof in the adjacent photosensitive layer, or is induced by chemical development or physical development in the adjacent layer of the certain specified photosensitive layer.
A third defect is that the sensitizing dye used diffuses from the photosensitive emulsion layer to which it is specific to the adjacent photosensitive emulsion layer to cause sensitization of the latter layer resulting in an unsuitable distribution of spectral sensitivity.
Due to these defects, the color forming reaction in a certain specified photosensitive emulsion layer adversely influences the adjacent photosensitive emulsion layer which should function independently. This causes the formation of corresponding color images to cause an overlap with the color images of the specified photosensitive emulsion layer, the so-called "color mixing".
As methods of improving these defects, methods have been suggested for decreasing the "color mixing" itself, for example, to provide an ML and an FL or to add reducible compounds to the ML -- for example, hydroquinone derivatives or phenol derivatives; scavengers for the oxidation products of the color developing agent; compounds which coupler to form colorless compounds or color couplers which form diffusible dyes; or agents for preventing diffusion of sensitizing dyes or couplers -- for example, finely divided silver halide particles, colloidal silica -- anionic, amphoteric, nonionic or cationic surface active agents, cationic hydrophilic polymers or polymer latexes, etc. However these approaches are not satisfactory.
Another method of improving the problem of "color mixing" is to introduce elements which have the function of "color correction."
A first such method comprises using colored couplers having a self-masking function. For example, known techniques and improvements therein are described in U.S. Pat. Nos. 2,449,966, 2,455,170, 2,600,788, 2,428,054, 3,148,062 and 2,983,608, and British Patent 1,044,778. However, this method can not be used for positive type color photosensitive materials because the method causes intense coloring in the non-exposed areas. This is because fog occurs due to the products formed by release of splitable azoaryl groups in the color development step and granularity of color images is deteriorated by such fog.
Secondly a method which comprises using the so-called "DIR coupler" is known. The term DIR coupler designates the couplers defined in C. R. Barr, J. R. Thirtle and P. W. Vittum, Photographic Science and Eng. Vol. 13, pages 74 -80 (1969) and 214 -217 (1969). By the use of the DIR coupler, effects caused by inhibition of development in the photosensitive emulsion layer used, such as an improvement of sharpness of color images by an edge effect or improvement of granularity, remarkably appear in predominance to the interlayer effect. It is known that the DIR coupler causes an interlayer effect. However, the DIR coupler has the defects that a deterioration of gradation (gamma) or a reduction of the maximum color density (D max) results because the DIR coupler causes a strong development inhibition effect in the centers of development depending on the image exposure - image development at the color development step. Accordingly, when the function of "color correction" related to the present invention must be effectively exhibited, it becomes necessary to use couplers which cause an interlayer effect which is stronger than the development inhibition effect in the layer. In the DIR coupler, the chemical structure of the compound which causes the effect in the layer rather than the interlayer effect can not be predicted from a mere knowledge of the chemical structure of the basic nucleus of known couplers or the chemical structure of splitable groups thereof. This is because the effect of "color correction" appears as a result of complicated factors such as the rate of the releasing coupling reaction of the DIR coupler, the development inhibition activity of the release splitable group, the diffusion property of the released splitable group in the photosensitive layer, the developing rate of each coexistent photosensitive emulsion itself, the coupling activity of the coupler coexistent or existent in other layers, the mutual interaction with compounds coexistent in the ML or the FL or the spectral absorption characteristic of colored dyes, or a combination of these factors.
The DIR coupler produces color dyes by color development. Accordingly, it is necessary that the colored dyes produced satisfy the requirements for the photosensitive layers used, and thus the DIR coupler has limited uses. Colorless DIR couplers are known and are described, for example, in U.S. pat. No. 3,632,345, and German Patent Publication (OLS) No. 2,060,196, etc. However, such a coupler has the tendency to contaminate if the photosensitive material used is stored for a long period of time.
Thirdly, a method which comprises using substantially fogged emulsions or direct positive emulsions, a method which comprises using internally fogged emulsions or internal latent image emulsions and a method which comprises utilizing the Luckey effect are known. However, these methods which comprise using such silver halide emulsions are accompanied by a reduction in sharpness due to the light scattering of their particles upon exposure, difficulties in controlling the photographic property of the emulsions and photographic subordinate actions.
Fourthly, a method of controlling the composition of each silver halide emulsion itself, such as the BL, GL or RL used in the superposed structure, for example the proportion of iodine ion content and bromine ion content, or controlling the interlayer distribution of materials having a development inhibiting property and controlling the interlayer distribution of materials having a developnent accelerating property in the antifogging agent or stabilizer used are known. However, sufficient "color correction" effect using these means is not obtained.
In addition, factors in the development treating process, for example, the developing agent content, the halogen ion content, the sulfide ion content and the hydrogen ion concentration in the developer, the buffer properties thereof and the degree of fatigue thereof, etc., are included. The effect of "color correction" by these factors also is not sufficient.
The above described hydroquinone derivatives react as a reducible compound and as a reducing agent for the color development agent in an oxidized state to render the products inactive to couplers and thus "color mixing" decreases. However, if the hydroquinones are present with the coupler, they inhibit color formation of the couplers to cause a reduction of D max or a loss of toe gradation.
It is known that hydroquinone derivatives are included in photosensitive emulsions as an activator for development. They are particularly used in black-white photosensitive materials. The hydroquinone derivatives function as a developing agent in black-white development. However, in color development of the photosensitive materials where they coexist with couplers, they function to inhibit color development. Accordingly, it is known that the function of the hydroquinone derivatives is quite different between their use in photosensitive materials for forming images by black-white development and their use in color development or between their use in photosensitive materials where they are coexistent with the couplers and where they are used in a very large amount in photosensitive materials.
Hydroquinone derivatives are known and used as IRD (inhibitor-releasing developers), for example, as described in U.S. Pat. No. 3,379,529. An IRD is a developer per se. Namely, an IRD is a developer which activates development and consequently releases an inhibitor. Accordingly, an IRD is useful in black-white development when it is used in a very large amount as compared with the couplers in the present invention. The function of an IRD remarkably deteriorates in color development when it is used in an amount comparable with the amount of couplers commonly used.
U.S. Pat. No. 3,620,746 discloses that hydroquinone derivatives are used as DIR hydroquinones. The disclosure of U.S. Pat. No. 3,620,746 relates to specified color photographic materials for recording light images on a braun tube for radar use (a phosphor-coated radar screen), which is characterized by using an anti-diffusion coupler and the so-called DIR coupler (developing inhibitor-releasing hydroquinone compound) in silver halide emulsions containing additionally fine silver halide grains and having a more rapidly developing property and particularly in chlorobromide emulsions. However, this element can not be used for improving the color reproduction, which is one of the objects of the present invention. In a color photographic sensitive material, if a specific photosensitive emulsion layer has the property of developing more rapidly, a gradation balance between the other photosensitive emulsion layers changes to result in very bad color reproduction. If it is not carried out according to the description of U.S. Pat. No. 3,620,746, namely if more rapidly developable emulsions are not used, not only does the effect described in the above described patent not appear but also the graduation and the D max of the colored images of the photosensitive layer containing the DIR hydroquinone deteriorates.